It is known to use arrangements of moderate-sized switch units to construct a high-capacity switch. A mesh interconnection of switch units is an efficient arrangement in comparison to cascaded multi-stage arrangements. A switch unit is a single-stage, non-blocking switching device having a plurality of input ports and a plurality of output ports. To provide fine granularity, time-sharing schemes, such as Time-Division-Multiplexing, may be used, and the switch units should have a low switching latency; on the order of a few nanoseconds, for example.
A core switch connecting distributed edge nodes may be based on an electronic switch fabric or an optical switch fabric. An edge node interfaces with data sources and sinks and is typically provided with buffers. An electronic-based core switch requires optical-electrical and electrical-optical interfaces with optical channels connecting the core switch to edge nodes or to other electronic-based core switches. An optical core switch switches optical signals without the need for optical-electrical and electrical-optical conversion. In addition, an optical core switch is compact and has the advantage of low power consumption.
There are, however, several challenges in constructing a large-scale, optical switch using a time-sharing scheme such as a conventional time-division-multiplexing scheme. While it is feasible to construct a slow-switching, optical switch unit of large dimension, 2000×2000 for example, a fast-switching, optical switch unit is limited to a relatively small dimension, 32×32, for example. This forces the use of multi-stage structures, such as a mesh structure, to construct a fast-switching, optical switch of large dimension. Due to the absence of buffers in the optical domain, at least with the present state of the art, establishing a connection through a time-shared, multi-stage structure requires a compound time-slot-matching process. A compound time-slot matching process of high order (third order or higher) may be computationally intensive and may also lead to relatively-low occupancy due to mismatch blocking as taught in the United States Patent Publication No. 2004/0037558 entitled “Modular High-Capacity Switch”.